The spectacle of Harper's signatories lining up to shame and dunk on those of their fellow signatories who've broken ranks with them is pretty intense.
It's gleeful, is what it is.
The assumption of bad faith that runs through the dunks is striking, too—the refusal to extend goodwill, to adopt a charitable reading of the tweet.
If I were a not-terribly-prominent signatory to the letter, and I honestly regretted having signed, the experience of seeing megafamous arts-and-letters superstars (and Jesse Singal) drag apostates might give me pause about saying so publicly.
And that's before you even get to the question of the torrent of harassment that inevitably follows a snotty callout from someone with this size of following.
As for what a charitable reading of the tweet might look like, I refer you to this thread of mine from yesterday, discussing why the list of signatories to an open letter is likely to (properly!) shape how people interpret the letter itself.
